Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• formation of alkenone intermediates, dialkyl acetylenedicarboxylates 147, as alkynoyl derivatives, are transformed to pyrazolones 149 by Michael addition–cyclocondensation with phenylhydrazine. In a consecutive one-pot reaction, the latter intermediates undergo O-acylation with aryl chlorides to give N

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• leaving groups. The eliminating agent (AcCl) led to O-acylation of the intermediate 14 and resulted in deoxygenation through the release of AcOH giving 2H-imidazole derivatives. On the other hand, in case of “addition–oxidation” (SNH AO, path B), the oxidant DDQ picked up a proton from intermediate 14 to

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• min. The authors propose that the reaction does not follow the mechanism of the Perkin process but proceeds via acylation of salicylaldehyde (44) to intermediate 45, which forms coumarin (46) in an intramolecular aldol cyclization. Therefore, O-acylation of salicylaldehyde (44) is completed at 150 °C

• 240 °C in one tube reactor, the reaction gives incomplete conversion and the yield of coumarin (46) drops to 21%. The authors proposed that under these conditions the reaction proceeds via the Perkin process, which is significantly slower than the O-acylation/aldol sequence [42]. An odorant that is

Synthesis of monophosphorylated lipid A precursors using 2-naphthylmethyl ether as a protecting group

• Jundi Xue,
• Ziyi Han,
• Gen Li,
• Khalisha A. Emmanuel,
• Cynthia L. McManus,
• Qiang Sui,
• Dongmian Ge,
• Qi Gao and
• Li Cai

Beilstein J. Org. Chem. 2020, 16, 1955–1962, doi:10.3762/bjoc.16.162

• - and 3,3′-O-acylation (Figure 1). The associated fatty acid acyl chains may be conserved within a species but can vary significantly in terms of the chain number and length for lipid A of different bacterial origins [3][4]. Lipid A represents a particularly important subject to research given the

Regioselectivity of glycosylation reactions of galactose acceptors: an experimental and theoretical study

• Enrique A. Del Vigo,
• Carlos A. Stortz and
• Carla Marino

Beilstein J. Org. Chem. 2019, 15, 2982–2989, doi:10.3762/bjoc.15.294

• by BF3·OEt2-promoted glycosylation [18] with a short reaction time, exploiting anchimeric assistance, followed by Zemplén de-O-acylation. On the other hand, for the synthesis of the α-anomer 8, a SnCl4-promoted glycosylation was found to be very effective [19], but with a longer reaction time in

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

• seemingly simple transformations needed for the assembly of lipid A, such as glycosylation towards fully orthogonally protected β(1→6)-linked diglucosamine backbone, sequential protective groups manipulation combined with successive instalment of multiple functional groups, N- and O-acylation with the long

• DBU to provide a free amino group, the 2’-NH2 and 3-OH groups could be differentiated in the next acylation step by using DCC as activating agent for the N-acylation, and Steglich reaction conditions (DCC and DMAP) for the O-acylation. Following removal of the Alloc protecting group was readily

Total synthesis of elansolids B1 and B2

• Liang-Liang Wang and
• Andreas Kirschning

Beilstein J. Org. Chem. 2017, 13, 1280–1287, doi:10.3762/bjoc.13.124

• iodide 17 after O-acylation, iodination of the terminal alkyne and finally diimide-mediated syn-reduction [11]. Next, DDQ-mediated removal of the PMB protecting group yielded vinyl iodide 18. The synthesis of both fragments 13 and 18 set the stage for the Suzuki–Miyaura coupling which delivered the

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• renders possible chemoselective O-acylation, furnishing the corresponding side-chain esters directly, on multigram-scale, in a single step, and without chromatographic purification. Assuming a certain degree of stability under acidic reaction conditions, the method is also applicable for a number of

• more elaborate procedures for chemoselective O-acylation reactions, spur its further development, and finally to chronicle the informative, but poorly documented history of its development. Keywords: amino alcohols; chemoselectivity; DOPA; hydroxyamino acids; hydroxyproline; O-acylation

• be distinctly preferable to other, including newer and more widely publicized, preparatory strategies for chemical manipulation of amino alcohols and other functionally related substances. Review The historical development of acidic chemoselective O-acylation procedures for hydroxyamino acids The

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• resolution of (±)-3 by using both Novozym 435 and Lipozyme TL IM preparations in the next optimization stages. Solvent effect on kinetic resolution of (±)-3 The next stage of enzymatic analytical scale studies was designed to find the most suitable co-solvent system for the enantioselective O-acylation of

Solution phase synthesis of short oligoribonucleotides on a precipitative tetrapodal support

• Alejandro Gimenez Molina,
• Amit M. Jabgunde,
• Pasi Virta and
• Harri Lönnberg

Beilstein J. Org. Chem. 2014, 10, 2279–2285, doi:10.3762/bjoc.10.237

• this was then used for the 3'-O-acylation of 4a in pyridine in the presence of 4-dimethylaminopyridine. Experimental details for the preparation of all the building blocks and NMR and MS data for their characterization are given in Supporting Information File 1. Oligonucleotide synthesis Previously

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• [30] and dynamic kinetic resolution [31]. However, in contrast to these routes, we desired to develop a synthesis of O-acylated (2S,3S)-3-hydroxyleucine derivatives which should be easily scalable and would enable O-acylation after construction of the stereocenters with only few changes in the

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens

• Yoshihiro Nishida,
• Yuko Shingu,
• Yuan Mengfei,
• Kazuo Fukuda,
• Hirofumi Dohi,
• Sachie Matsuda and
• Kazuhiro Matsuda

Beilstein J. Org. Chem. 2012, 8, 629–639, doi:10.3762/bjoc.8.70

• glycerol sn-1 position. Then, this compound was converted to glycolipid 8a after sequential reaction of the temporary tert-butyldimethylsilyl (TBDMS) -protected sugar, and O-acylation at the glycerol 2-OH position to give 7a, followed by removal of the TBDMS protecting group. For introducing the

N-acylation of ethanolamine using lipase: a chemoselective catalyst

• Mazaahir Kidwai,
• Roona Poddar and
• Poonam Mothsra

Beilstein J. Org. Chem. 2009, 5, No. 10, doi:10.3762/bjoc.5.10

• lipase (Novozym® 435) are described and optimum conditions for selective N-acylation rather than O-acylation are also discussed. Microwave assisted solution phase, solid supported and conventional methods were investigated and results were compared. There is a synergy between the enzyme catalysis and

• acylations, O-acylation and N-acylations, the latter is more favoured in aminoalkanol NH2(CH2)nOH because the amino residue serves as a better nucleophile than the hydroxy group. The selectivity of the aminoalkanol NH2(CH2)nOH towards N-acylation rather than O-acylation is attributed to following reasons (i

Synthesis of phosphorothioates using thiophosphate salts

• Babak Kaboudin and
• Fatemeh Farjadian

Beilstein J. Org. Chem. 2006, 2, No. 4, doi:10.1186/1860-5397-2-4

• benzoyl chloride (a hard electrophile), gave the O-acylation product. A simple, efficient, and general method has been developed for the synthesis of phosphorothioates through a one-pot reaction of alkyl halides with the mixture of diethyl phosphite in the presence of triethylamine/sulfur/and acidic

• by reaction of diethylphosphite, sulfur and triethyl amine. [54][55][56][57] We found that reaction of triethylammonium O,O'-diethyl thiophosphate with benzoyl chloride gave benzoyl O,O'-diethyl phosphorothioate with O-acylation product (Scheme 6). We conclude that replacement of benzyl with benzoyl

• group (hard electrophilic center) gives the O-acylation product. As a part of our efforts to explore the utility of surface-mediated reactions for the synthesis of organophosphorus compounds, [16][17][18] herein we report a new method for the preparation of phosphorothioates by reaction of diethyl